Several different types of secondary batteries are widely used and are commercially applicable as a rechargeable electrochemical energy storage system. Among these secondary batteries, a secondary lithium battery provides advantages in high performance due to the high power capacity and energy density. The use of the secondary lithium battery is important in portable electronic devices such as mobile phones, laptops, digital cameras, and video camcorders. In addition, a secondary lithium battery is a great power source for automotive, hybrid cars, and electric bicycles (e-bikes), which is expected to be used effectively as a promising energy storage system (ESS) in the future. With recent technology trends, there is significant ongoing research and development in an innovative secondary lithium battery to improve the capacity and operating voltage, and in particular, designing a new electrode material.
In particular, an innovative concept of a new electrode material is unavoidable, because a significantly improved performance of secondary lithium battery generally originates from the improvement in the design and physical/chemical characteristics of the cathode and anode. On the other hand, the conventional cathode and anode have been fabricated by the following steps. First, slurry is prepared by mixing an active material, a conductive material, and a binder. The slurry is then applied on a metallic current collector in the form of a thin film, which is subsequently dried and pressed at room temperature, finally producing the cathode and anode electrodes. In this case, the current collector plays a vital role as an electrode support along with an electron acceptor and donor. It is therefore highly desirable to enlarge the contact area and minimize the contact resistance between the metallic current collector and active material in order to improve electrode performance by accepting or donating electrons as efficiently as possible.
In this respect, the conventional electrode mentioned above may not have sufficiently good adhesion to bond a coating layer to the current collector film, which can cause a problem of increasing the contact resistance due to exfoliation of the coated material from the current collector. Moreover, during the actual charging and discharging cyclic operations, the powder materials degrade and fall off due to stresses caused by volume expansion. Additionally, the binder is electrically non-conductive and generally degrades the conductivity of the electrode. The present invention relates solutions to overcome the limitations as stated above. An aspect of the invention is to use porous metal foam as an electrode, which can accommodate stresses and strains developed during charging/discharging cycling.
Therefore there is a need for a secondary lithium battery with metal foam electrode.